KR20180060777A - Electrode assembly and rechargeable battery including the same - Google Patents

Abstract

According to an embodiment of the present invention, a windable electrode assembly comprises: a negative electrode and a positive electrode respectively comprising a base material and a first laminate and a second laminate which are respectively formed on both sides of the base material; and a separator positioned between the positive electrode and the negative electrode. The first laminate of the negative electrode is located relatively farther from the center of the electrode assembly than the second laminate of the positive electrode, and the first laminate in the negative electrode is oriented with respect to one surface of the base material of the negative electrode.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode assembly and a secondary battery including the electrode assembly.

The present invention relates to an electrode assembly, and more particularly, to an electrode assembly for a secondary battery and a secondary battery including the electrode assembly.

A lithium secondary battery, which has recently been spotlighted as a power source for portable electronic devices, has a discharge voltage twice as high as that of a conventional battery using an alkaline aqueous solution, resulting in high energy density.

The secondary battery may include an electrode assembly in which a negative electrode, a separator, and an anode are repeatedly laminated, or a jelly roll type electrode assembly formed by laminating a negative electrode, a separator, and an anode and winding them. Since the jelly roll electrode assembly repeatedly forms the negative electrode, the separator and the positive electrode, nonuniform reaction may occur due to different circumferences from the center to the outer periphery of the electrode assembly.

If the reaction between the anode and the cathode is uneven, the lifetime of the secondary battery may be reduced due to a partial phenomenon such as overcharging or overvoltage.

Accordingly, it is an object of the present invention to provide an electrode assembly and a secondary battery capable of increasing the lifetime of the secondary battery by making the reaction in the secondary battery uniform.

A wound electrode assembly according to an embodiment of the present invention includes a base, a negative electrode and a positive electrode each including a first composite and a second composite formed on both sides of the base, and a separator positioned between the negative and positive electrodes, The first composite of the cathode is located relatively farther from the center of the electrode assembly than the second composite of the cathode and the first composite of the cathode is oriented with respect to one surface of the substrate of the cathode.

The first composite of the anode may be positioned relatively closer to the center of the electrode assembly than the second composite of the anode.

The first composite of the negative electrode and the first composite of the positive electrode are located opposite to each other with the separator interposed therebetween and the first composite of the negative electrode may be located adjacent to the center of the electrode assembly relative to the first composite of the positive electrode.

The second composite of the cathode and the second composite of the anode may be located opposite to each other with the separator therebetween and the second composite of the anode may be located relatively closer to the center of the electrode assembly than the second composite of the cathode.

The first and second composites of the negative electrode include a carbon-based negative active material, and the first and second composites of the negative electrode have a degree of divergence (DD) value defined by the following formula (1). The difference between the first DD value of the first composite and the second DD value of the second composite may be 10 or more. At this time, the DD value of the first composite of the cathode may be 19 or more and 60 or less, and the DD value of the second composite of the cathode may be 5 or more and less than 19.

[Formula 1]

DD (Degree of Divergence) = (I _a / I _total ) x 100

(In the above formula 1,

I _a is the sum of peak intensities at non-planar angles in XRD measurement using CuKα line,

I _total is the sum of the peak intensities at all angles in XRD measurement using CuKα line).

The carbonaceous anode active material may be a mixture of artificial graphite or artificial graphite and natural graphite, or a mixture of graphite and a Si-based, Sn-based or LiMOx (M = metal) system. The electrode assembly may further include a center pin, and the electrode assembly may be wound around the center pin.

The secondary battery according to another embodiment of the present invention includes the electrode assembly, a case for housing the electrode assembly, and an electrolyte contained in the case together with the electrode assembly.

1 is a cross-sectional view of a secondary battery according to an embodiment of the present invention.
2 is a cross-sectional view illustrating a portion of the electrode assembly of FIG.
3 is a schematic view for explaining the orientation of the negative electrode active material according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

The sizes and thicknesses of the respective components shown in the drawings are arbitrarily shown for convenience of explanation, and thus the present invention is not necessarily limited to those shown in the drawings.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. In the drawings, for the convenience of explanation, the thicknesses of some layers and regions are exaggerated. Whenever a portion such as a layer, film, region, plate, or the like is referred to as being "on" or "on" another portion, it includes not only the case where it is "directly on" another portion but also the case where there is another portion in between.

Also, throughout the specification, when an element is referred to as " including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise.

FIG. 1 is a cross-sectional view of a secondary battery according to an embodiment of the present invention, FIG. 2 is a cross-sectional view illustrating a portion of the electrode assembly of FIG. 1, and FIG. 3 is an exploded perspective view of an anode active material according to an embodiment of the present invention. Fig.

1, a secondary battery according to an embodiment of the present invention includes an electrode assembly 10, a case 20 housing the electrode assembly 10, and a gasket interposed between the case 20 and the case 20, A cap assembly 30 electrically connected to the electrode assembly 10 and an insulating plate 50 provided between the cap assembly 30 and the electrode assembly 10 and a center pin 60).

The electrode assembly 10 includes a positive electrode 11, a separator 12 and a negative electrode 13 which are sequentially stacked. The separator 12 is disposed between the positive electrode 11 and the negative electrode 13 and insulates them from each other. The electrode assembly 10 may be a cylindrical jelly roll formed by laminating the positive electrode 11, the separator 12, and the negative electrode 13 and then winding the center pin 60 around the center electrode.

The separator 12 may be a polyethylene / polypropylene double layer separator, a polyethylene / polypropylene / polyethylene three layer separator, a polypropylene / polyethylene / polypropylene double layer separator, A polypropylene three-layer separator, or the like can be used.

The positive electrode 11 and the negative electrode 13 are made up of electrode active portions 11a and 13a which are regions coated with an active material on a thin plate formed of a metal foil and electrode uncoated portions 11b and 13b which are regions where no active material is applied, . The electrode uncoated portion 11b of the positive electrode and the electrode uncoated portion 13b of the negative electrode may be located at opposite ends of the electrode assembly 10.

Specifically, referring to FIG. 2, the electrode active portion 11a of the anode can be formed by applying a positive electrode composite material 11aa made of a positive electrode active material onto a first base material 11ab made of a metal foil such as aluminum. The positive electrode composite material may include a first composite material (11aa1) and a second composite material (11aa2) formed on both surfaces of the first base material.

As the cathode active material, a compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound) can be used. For example, at least one of composite oxides of lithium and metal selected from cobalt, manganese, nickel, and combinations thereof may be used. In the positive electrode, the content of the positive electrode active material may be 90% by weight to 98% by weight based on the total weight of the positive electrode composite material.

In one embodiment of the present invention, the positive electrode composite material 11aa may further include a binder and a conductive material. At this time, the content of the binder and the conductive material may be 1 wt% to 5 wt% with respect to the total weight of the positive electrode composite material.

The binder serves to adhere the positive electrode active materials to each other and to adhere the positive electrode active material to the current collector. Representative examples of the binder include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymer containing ethylene oxide, polyvinyl pyrrolidone But are not limited to, polyurethane, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy resin, nylon and the like.

The conductive material is used for imparting conductivity to the electrode. Any conductive material may be used for the battery without causing any chemical change.

And. The electrode active portion 13a of the negative electrode can be formed by applying a negative electrode material 13aa made of graphite or an active material such as carbon to the second base material 13ab made of a metal foil such as copper or nickel. The negative electrode composite material 13aa may include a first composite material 13aa1 and a second composite material 13aa2 formed on both surfaces of the second base material 13ab.

The anode material 13aa may include a carbonaceous anode active material and the first material 13aa1 and the second material 13aa2 may have a degree of divergence (DD) value defined by Equation 1 below. The DD value of the first member may be 19 or more and 60 or less, and the DD value of the second member may be 5 or more and less than 19.

[Formula 1]

DD (Degree of Divergence) = (I _a / I _total ) x 100

In Equation (1)

I _a is the sum of peak intensities at non-planar angles in XRD measurement using CuKα line,

I _total is the sum of peak intensities at all angles in XRD measurement using CuKα line.

In this case, the non-planar angle represents 2θ = 42.4 ± 0.2 °, 43.4 ± 0.2 °, 44.6 ± 0.2 °, and 77.5 ± 0.2 ° when XRD measurement using CuKα line, ie, (100) R plane, (101) H plane, and (110) plane . Generally, graphite is classified into a hexagonal structure and a rhombohedral structure having an ABAB stacking sequence according to stacking order of a graphene layer, and the R The face means the Lombo headular structure, and the H plane means the hexagonal structure.

In the XRD measurement using CuK? Ray, all the angles indicate 2? = 26.5? 0.2, 42.4? 0.2, 43.4? 0.2, 44.6? 0.2, 54.7? 0.2 and 77.5? It represents the (002) plane, (100) plane, (101) R plane, (101) H plane, (004) plane and (110) plane. The peak appearing at 2θ = 43.4 ± 0.2 ° may be seen as overlapping peaks corresponding to the (111) plane of the current collector, for example, Cu, with the (101) R surface of the carbonaceous material.

Generally, the peak intensity value refers to the peak height value or the integrated area value of the peak, and the peak intensity value according to one embodiment means the integral area value of the peak.

In one embodiment of the present invention, the XRD measurement is performed using a CuKα line as a target line. In order to improve the peak intensity resolution, a target line is extracted using a monochromator device Respectively. In this case, the measurement conditions were measured at a measurement condition of 2? = 10 to 80 and a scan speed (? / S) of 0.044 to 0.089 and a step size of 0.026 占 / step.

The DD value according to an embodiment of the present invention is a value obtained by charging / discharging a lithium secondary battery including the negative electrode and then measuring the XRD of the negative electrode obtained by dismantling the battery in a fully discharged state. At this time, the charge and discharge conditions were 0.1 to 0.2C and one to two times.

The peak intensity ratio of the (004) plane of the negative electrode, that is, I ₍₀₀₄₎ / I ₍₀₀₂₎ may be 0.04 or more and 0.04 or more and 0.07 ≪ / RTI > When the I ₍₀₀₄₎ / I ₍₀₀₂₎ of the negative electrode is 0.04 or more, the DC internal resistance is not increased, and the rate characteristics, especially the high rate characteristics, can be improved and the cycle life characteristics can be improved.

The DD value according to an embodiment of the present invention indicates the degree to which the negative active material of the first composite material 13aa1 and the second composite material 13aa2 of the negative electrode are oriented with a certain angle. The difference in the second DD value of the second member may be 10 or more. At this time, the DD value of the first member 13aa1 is 19 or more and 60 or less, and the DD value of the second member 13aa2 may be 5 or more and less than 19. For example, if the DD value of the first member 13aa1 is 19, the DD value of the second member 13aa2 is 9 or less, and the DD value of the second member 13aa2 is 18, then the first member 13aa1, The DD value may be 28 or more.

This indicates that the negative active material of the first composite 13aa1 is relatively more oriented than the negative active material of the second composite 13aa2. At this time, the first member 13aa1 may be located farther from the center of the electrode assembly 10 than the second member 13aa2 about the second substrate 13ab. This value is the property value maintained even after charging / discharging.

As shown in Fig. 3, in order to orient the first aggregate 13aa1 of the negative electrode, the negative active material may be coated on the second base material and then oriented using a magnetic field. At this time, the degree of orientation can be controlled by adjusting the intensity of the magnetic field, the exposure time of the magnetic field, the viscosity of the negative electrode active material composition, the rolling strength, and the density of the compound. For example, when 97.5% by weight of artificial graphite, 1.5% by weight of styrene-butadiene rubber, and 1% by weight of carboxymethyl cellulose are mixed in an aqueous solvent, the viscosity (here, temperature is 25 ° C) cps. < / RTI >

Then, the Cu foil is placed on the magnet having a magnetic field strength of 4,000 Gauss, and then the negative electrode active material slurry is coated on the Cu foil and exposed to a magnetic field for 9 seconds. Thereafter, when the magnetic field is removed and the negative electrode active material slurry is dried and rolled, a first mixture having a DD value of 39 can be produced. On the other hand, if the prepared slurry of the negative active material is coated on a Cu foil, dried, and then rolled, a second member having a DD value of 18 can be produced.

Magnetic flux generated by the magnet is formed in a direction perpendicular to the negative electrode base, but the direction in which the magnetic field is formed depends on the coating rate (moving speed of the negative electrode base material) ) Function. Therefore, the negative electrode active material contained in the negative electrode active material composition may be formed to have a certain angle with respect to the surface of the negative electrode base material, that is, to be oriented.

Also, as in the embodiment of the present invention, when the DD value of the first composite material 13aa1 of the negative electrode is 19 or more and 60 or less, the negative electrode active material does not lie horizontally on one surface of the second base material 13ab, Means that the lithium ion is sufficiently oriented to facilitate the movement of Li ions in the cathode. Therefore, the second composite material 13aa2 having a relatively smaller DD value as compared with the first composite material 13aa1 is more oriented than the first composite material 13aa1. The second member 13aa2 may not be subjected to a separate orientation process after application of the negative electrode active material. Therefore, as compared with the first member 13aa1, the second member 13aa2 can not move the Li ions relatively smoothly, so that the DC internal resistance can be large.

Referring again to FIG. 2, in the formation of a circular jelly roll, the first member 13aa1 of the cathode is positioned adjacent to the center of the electrode assembly 10 relative to the first member 11aa1 of the anode Considering the radius of curvature, there may be a risk that deterioration such as lithium precipitation may occur due to a larger N / P ratio (anode capacity / cathode capacity) due to a larger area of the anode against the cathode.

Accordingly, in the present invention, the degree of orientation of the first composite material (13aa1) of the negative electrode which is located closer to the center of the electrode assembly (10) relative to the first composite material (11aa1) of the positive electrode is increased, By reducing the resistance, deterioration such as lithium precipitation, which may be caused by a relatively low N / P ratio, is suppressed, so that not only safety but also life of the secondary battery can be increased.

Since the positive electrode 11, the separator 12 and the negative electrode 13 are repeatedly wound around the electrode assembly 10, the first composite material 13aa1 of the negative electrode and the first composite material 11aa1 of the positive electrode are separated from the separator 12 And the first member 13aa1 of the cathode may be positioned adjacent to the center of the electrode assembly 10 relative to the first member 11aa1 of the anode . The second composite material 13aa2 of the negative electrode and the second composite material 11aa2 of the positive electrode may be disposed opposite to each other with the separator 12 therebetween. At this time, the second composite material 11aa2 of the positive electrode (See portion B) relative to the center of the electrode assembly 10 relative to the center electrode 13aa2.

When the lithium secondary battery is charged, lithium ions are discharged from the anode and inserted into the cathode. At this time, when the site in the cathode which can receive the lithium ions from the anode is small, problems such as lithium precipitation occur. This problem is caused by the loading level (L / L) of the anode / cathode plate and the resistance increase during the reaction.

Accordingly, the negative electrode capacity of the electrode assembly 10 is formed to be larger than the positive electrode capacity, and the N / P ratio, which is a numerical value thereof, has a value of 1.0 to 1.2 in a general lithium secondary battery. In the electrode assembly 10, which is repeatedly wound like a cylindrical battery, the anode capacity is relatively large in comparison with the anode capacity (A, eg N / P = 1.05) There may be a very large area (B, eg N / P = 1.10). This is because the electrode assembly 10 is repeatedly wound and formed so that the circumferences of the cathode and the anode are different. In the present invention, in the region A where the anode capacity is relatively larger than the anode capacity, Is arranged so that the first member (13aa1) of the first member

The first laminate 13aa1 of the negative electrode is oriented in a certain direction as compared with the second laminate 13aa2 of the negative electrode so that the movement of Li is easier than the second laminate 13aa2 of the negative electrode, Is increased.

On the other hand, the BET specific surface area of the negative electrode composite material may be less than 3.0 m 2 / g, and may also be 0.6 m 2 / g to 1.2 m 2 / g. When the BET specific surface area of the negative electrode material mixture 13aa is less than 3.0 m 2 / g, the electrochemical lifetime characteristics of the cell may be improved .

The BET measurement was performed by charging / discharging the lithium secondary battery including the negative electrode, dismantling the battery in a completely discharged state, cutting the negative electrode into a predetermined size, placing it in a BET sample holder and measuring it with a nitrogen gas adsorption method will be.

The negative electrode may have a single-sided loading level (L / L) of 6 mg / cm ² to 65 mg / cm ² .

The carbonaceous anode active material may be artificial graphite or a mixture of artificial graphite and natural graphite. When a crystalline carbon-based material, which is a mixture of artificial graphite or artificial graphite and natural graphite, is used as the negative electrode active material, the crystallographic characteristics of the particles are more improved than those of the amorphous carbon-based active material, It may be advantageous to further improve the orientation property of the carbon material. The form of the artificial graphite or natural graphite may be amorphous, plate-like, flake, spherical, fibrous, or a combination thereof, and may be in any form. When the artificial graphite and the natural graphite are mixed, the mixing ratio may be 70:30 to 95: 5 wt%.

In addition, the negative electrode material may further include at least one of a Si-based negative active material, a Sn-based negative active material, or LiMOx (M = metal). In the case where the negative electrode mixture further includes the carbonaceous negative electrode active material as the first negative electrode active material and the negative electrode active material as the second negative electrode active material, the mixing ratio of the first negative electrode active material and the second negative electrode active material is 50: 99: 1 by weight.

The LiMOx (M = metal) anode active material may be lithium vanadium oxide.

The Si-based negative active material may be at least one selected from the group consisting of Si, Si-C composite, SiO _x (0 <x <2), Si-Q alloy (Q is an alkali metal, an alkali earth metal, a Group 13 element, a Group 14 element, Wherein the Sn-based negative electrode active material is Sn, SnO ₂ , Sn-R alloy (wherein R is an alkali metal, an alkali earth metal, , An element selected from the group consisting of a Group 13 element, a Group 14 element, a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and combinations thereof, and is not Sn) And SiO ₂ may be mixed and used. The element Q and the element R may be at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Pb, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

The content of the negative electrode active material in the negative electrode material mixture 13aa may be 95% by weight to 99% by weight based on the total weight of the negative electrode material mixture.

The negative electrode material mixture 13aa includes a binder, and may optionally further include a conductive material. The content of the binder in the negative electrode material may be 1 wt% to 5 wt% with respect to the total weight of the negative electrode material. When the conductive material is further included, the negative electrode active material may be used in an amount of 90 to 98 wt%, the binder may be used in an amount of 1 to 5 wt%, and the conductive material may be used in an amount of 1 to 5 wt%.

The binder serves to adhere the negative electrode active material particles to each other and to adhere the negative electrode active material to the negative electrode substrate well. As the binder, a non-aqueous binder, an aqueous binder, or a combination thereof may be used.

Examples of the non-aqueous binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer including ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride , Polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

Examples of the water-based binder include styrene-butadiene rubber, acrylated styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, ethylene propylene copolymer, polyepichlorohydrin, Polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, acrylate-based resin, or a mixture thereof. Combinations.

When an aqueous binder is used as the negative electrode binder, a cellulose-based compound capable of imparting viscosity may be further contained as a thickener. As the cellulose-based compound, carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, alkali metal salts thereof or the like may be used in combination. As the alkali metal, Na, K or Li can be used. The content of the thickener may be 0.1 part by weight to 3 parts by weight based on 100 parts by weight of the negative electrode active material.

The conductive material is used for imparting conductivity to the electrode. Any conductive material may be used for the battery without causing any chemical change. Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black and carbon fiber; Metal powders such as copper, nickel, aluminum, and silver, or metal-based materials such as metal fibers; Conductive polymers such as polyphenylene derivatives; Or a mixture thereof may be used.

Referring again to FIG. 1, the electrode assembly 10 may be contained in a case 20 together with an electrolyte, and the electrolyte includes a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

The lithium salt is dissolved in an organic solvent to act as a source of lithium ions in the cell to enable operation of a basic lithium secondary battery and to promote the movement of lithium ions between the anode and the cathode. The lithium salt Representative examples are _{LiPF 6, LiBF 4, LiSbF 6} , LiAsF 6, LiN (SO 2 C 2 F 5) 2, Li (CF 3 SO 2) 2 N, LiN (SO 3 C 2 F 5) 2, _{LiC 4 F 9 SO 3, LiClO} 4, LiAlO 2, LiAlCl 4, LiN (C x F 2x + 1 SO 2) (C y F 2y + 1 SO 2) ( where, x and y are natural numbers, e.g. 1 to 20), LiCl, LiI and LiB (C ₂ O ₄ ) ₂ (lithium bis (oxalato) borate: LiBOB) The concentration of the lithium salt is preferably in the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has an appropriate conductivity and viscosity, Lithium ions can move effectively.

In the jelly roll state, the positive electrode current collector plate 11d is connected to the electrode uncoated portion 11b of the positive electrode of the electrode assembly 10, and the negative electrode current collector plate 13d is connected to the negative electrode of the electrode assembly 10 And connected to the non-coated portion 13b.

The positive electrode current collector plate 11d is formed to be narrower than the negative electrode current collector plate 13d so that the negative electrode current collector plate 13d is in contact with the case 20 while the positive electrode current collector plate 11d is in contact with the case 20 .

A lead tab 37 is electrically connected to the positive electrode current collector plate 11d. One end of the lead tab 37 may be welded to the positive electrode current collector plate 11d and the other end may be electrically connected to the cap assembly 30. The lead tabs 37 may be bent so as to face one surface of the electrode assembly 10 in order to increase the contact area with the cap assembly 30. [

On the positive electrode collector plate 11d, an insulating plate 50 having an opening exposing the center pin 60 is located. The insulating plate 50 is formed to be larger than the anode current collector plate 11d so that the insulating plate 50 can contact the inner surface of the case 20. If the insulating plate 50 is formed larger than the positive electrode current collecting plate 11d as described above, a certain gap is formed between the positive electrode current collecting plate 11d and the case 20 by the width of the insulating plate 50 protruding out of the positive electrode current collecting plate 11d . The gap between the positive electrode current collector plate 11d and the case 20 can prevent the shape in which the positive electrode current collector plate 11d and the case 20 come into contact with each other to short-circuit.

The lead tab 37 may be connected to the first auxiliary plate 34 of the electrode assembly 10 to be described later through the opening 51 of the insulating plate 50. [

Since the electrode assembly 10 is wound around the center pin 60, the center pin 60 is positioned at the center of the electrode assembly 10 and is aligned with the direction in which the electrode assembly 10 is inserted into the case 20 . The center pin 60 maintains a shape that is at least deformed or approximates to the shape before deformation when subjected to a whole surface compression load or a local impact load acting on the outside of the secondary battery, .

The center pin 60 may be formed of a material having a predetermined stiffness, for example, a metal, so as to be minimally deformed against an external impact. When the center pin 60 is a metal having conductivity, both ends of the center pin 60 are installed to be electrically insulated from the positive electrode current collector plate 11d and the negative electrode current collector plate 13d.

For example, the insulating pad 52 may be disposed between the lower end of the center pin 60 and the corresponding negative electrode collector plate 13d. The upper end of the center pin 60 passes through the through hole formed at the center of the positive electrode current collector plate 11d in an insulated state and is supported on the insulating plate 50. At this time, the upper end of the center pin 60 may be spaced apart from the through-hole of the cathode current collector plate 11d, or an insulating member (not shown) may be interposed between the center pin 60 and the cathode current collector plate 11d. Therefore, the flow of the center pin 60 in the longitudinal direction of the center pin 60 is limited, and the center pin 60 can be maintained in a stable state at the center of the electrode assembly 10.

The case 20 may be formed so as to have substantially the same shape as the electrode assembly 10 and open at one side so that the electrode assembly 10 can be inserted therein. For example, the case 20 may be cylindrical . The case 20 is connected to the negative electrode current collecting plate 13d of the electrode assembly and can serve as a negative terminal of the secondary battery. Therefore, the case 20 can be formed of a conductive metal such as aluminum, aluminum alloy, or nickel-plated steel.

The cap assembly 30 is located in the opening of the case 20 and is coupled to the case 20 with the gasket 40 therebetween. The gasket 40 insulates the case 20 from the cap assembly 30 and seals the inside of the case 20 accommodating the electrode assembly 10 and the electrolyte.

Specifically, the cap assembly 30 includes a cap plate 31, a positive temperature coefficient element 35, a vent plate 32, an insulating member 33, a first sub-plate 34, And an auxiliary plate (38).

The first auxiliary plate 34 is electrically connected to the lead tab 37 of the electrode assembly and can be coupled to the lead tab 37 by welding.

The second auxiliary plate 38 is stacked on the first auxiliary plate 34 and is electrically connected to the first auxiliary plate 34 and can be coupled to the first auxiliary plate 34 by welding. The second auxiliary plate 38 is located at the center of the electrode assembly 10 corresponding to the center pin 60 and has a through hole exposing the first auxiliary plate 34.

The vent plate 32 is positioned above the second auxiliary plate 38 with the insulating member 33 therebetween. The edge of the vent plate 32 can be inserted into the gasket 40 and coupled to the case 20. [

The vent plate (32) includes a vent (32a) located at a portion corresponding to the center pin (60). The vent 32a protrudes from the vent plate 32 toward the electrode assembly 10 and is electrically connected to the first auxiliary plate 34 through the through hole. The vent plate 32 may have a notch 32b around the vent 32a to guide breakage of the vent 32a.

The vent 32a may be broken under a predetermined pressure condition to release the internal gas to the outside and cut off the electrical connection with the first auxiliary plate 34. [ That is, when the internal pressure of the case 20 rises due to the generation of the gas, the notch 32b is broken beforehand and the gas is discharged to the outside through the exhaust port 31d described later, thereby preventing the secondary battery from exploding.

In addition, if the vent 32a is broken due to the adverse reaction, the electrical connection between the vent plate 32 and the first auxiliary plate 34 is broken. Accordingly, the electrical connection between the cap plate 31 electrically connected to the vent plate 32 and the first auxiliary plate 34 is broken, and no further current flow occurs.

The cap plate 31 has a center plate 31a corresponding to the center pin 60 which is the center of the electrode assembly 10, a plurality of branch portions 31b extending from the center plate 31a toward the gasket 40, And an engaging plate 31c connected to the gasket 40 and coupled to one end of the gasket 31b. Between adjacent branch portions 31b, there is formed an exhaust port 31d that is opened to the outside and discharges the internal gas.

The branch portion 31b may be bent from the coupling plate 31c and connected to the center plate 31a so that the center of the cap plate 31 protrudes from the case 20. The cap plate 31 is electrically connected to the positive electrode collector plate 11d through the vent plate 32, the second auxiliary plate 38, the first auxiliary plate 34 and the lead tab 37, As shown in Fig. Therefore, if the center of the cap plate 31 is protruded to the outside of the case 20, terminal connection with an external device can be facilitated.

Meanwhile, the PTC device may be formed along the second plate of the cap plate 31, and may be inserted into the gasket 40 while being stacked between the second plate of the cap plate and the edge of the vent plate.

The positive temperature element 35 is provided between the cap plate 31 and the vent plate 32 so that the current flow can be interrupted between the cap plate 31 and the vent plate 32 according to the internal temperature of the secondary battery have.

When the internal temperature is within the predetermined range, the positive temperature element 35 acts as a conductor and electrically connects the cap plate 31 and the vent plate 32. However, when the internal temperature exceeds a predetermined temperature, the positive temperature element 35 has an electrical resistance that increases to infinity. Therefore, the positive temperature element 35 can block the flow of charging or discharging current between the cap plate 31 and the vent plate 32.

The edge of the cap assembly 30 is inserted into the opening of the case 20 after being inserted into the gasket 40 in a laminated form of the vent plate 32, the positive temperature element 35 and the cap plate 31. And the cap assembly 30 is clamped to the opening of the case 20 through a clamping process. The case 20 is provided with a beading portion 21 which is recessed in the radial center of the case 20 and a clamping portion 22 which catches the outer circumference of the gasket 40 into which the cap assembly 30 is inserted .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, And it goes without saying that the invention belongs to the scope of the invention.

10: electrode assembly 11: anode
11a, 13a: electrode active portion 11b, 13b: electrode non-
11aa: positive electrode composite material 11aa1, 13aa1: first composite material
11aa2, 13aa2: second member 11ab: first substrate
11d: positive electrode current collector plate 12: separator
13: cathode 13aa: cathode composite
13ab: second substrate 13d: negative electrode collector plate
20: Case 21:
22: clamping part 30: cap assembly
31: cap plate 31a: center plate
31b: branch portion 31c: engaging plate
31d: exhaust port 32: vent plate
31a: vent 32b: notch
33: Insulating member 34: First auxiliary plate
35: positive temperature element 37: lead tab
38: second auxiliary plate 40: gasket
50: insulating plate 51: opening
52: Insulation pad 60: Center pin

Claims (10)

In the wound electrode assembly,
The electrode assembly includes a base material, a negative electrode and a positive electrode each including a first mixture and a second mixture formed on both sides of the base material,
A separator disposed between the cathode and the anode,
Lt; / RTI &gt;
The first composite of the cathode being located farther from the center of the electrode assembly relative to the second composite of the cathode,
Wherein the first mixture of the negative electrodes is oriented with respect to one surface of the base material of the negative electrode. The method of claim 1,
Wherein the first composite of the anode is positioned adjacent to the center of the electrode assembly relative to the second composite of the anode. 3. The method of claim 2,
The first composite of the negative electrode and the first composite of the positive electrode are located opposite to each other with the separator interposed therebetween,
Wherein the first composite of the negative electrode is positioned adjacent to the center of the electrode assembly relative to the first composite of the positive electrode. 3. The method of claim 2,
The second composite of the negative electrode and the second composite of the positive electrode are located opposite to each other with the separator interposed therebetween,
Wherein the second composite of the anode is positioned adjacent to the center of the electrode assembly relative to the second composite of the cathode. The method of claim 1,
Wherein the first and second composites of the negative electrode comprise a carbon-based negative active material,
The first and second members of the negative electrode have a degree of divergence (DD) value defined by the following formula 1, and the difference between the DD value of the first composite of the negative electrode and the DD value of the second composite is 10 or more Assembly.
[Formula 1]
DD (Degree of Divergence) = (I _a / I _total ) x 100
(In the above formula 1,
I _a is the sum of peak intensities at non-planar angles in XRD measurement using CuKα line,
I _total is the sum of the peak intensities at all angles in XRD measurement using CuKα line). The method of claim 5,
Wherein the DD value of the first composite is between 19 and 60 and the DD value of the second composite is between 5 and 19. The method of claim 5,
Wherein the carbonaceous anode active material comprises a mixture of artificial graphite or artificial graphite and natural graphite. 8. The method of claim 7,
Wherein the carbonaceous anode active material further comprises at least one of Si, Sn, and LiMOx (M = metal). The method of claim 1,
Wherein the electrode assembly further comprises a center pin,
Wherein the electrode assembly is wound around the center pin. 10. An electrode assembly according to any one of claims 1 to 9,
A case for housing the electrode assembly,
The electrolyte contained in the case with the electrode assembly
And a secondary battery.

Images